Self-fitting key device



Dec. 26, 1922. Y

R. A. SMITH. SELF FlTTlNG KEY DEVICE.

FILED JULY 12, 1921 an van 6oz of the key. In some cases also the cutting Patented ea. 26, 19.22.

tree" STATES P'ATENT 0mm ROBERT a. SMITH, or MAHWAH, NEW, annsnxnssrenon 'ro sMIrrH & SEER-ELL, on MAHWAH, NEW JERSEY, A coPAarnnn-srnr consrsrrne or SAID ROBERT A.

SMITH AND JOHN J'. SERBELL.

-SELF-EITTING KEY DEVICE. q

i I Application fileaaul 12, 1921, Serial No, 484,094. Renewed July 26, 1922; sw m. 577,737. c

To all whom itimay 00mm k p Be it known that I, ROBERT A. SMITH, a citizen of the United States, and resident of Mahwah, Bergen County, State of'New Jersey, have made a certain new and useful Invention Relating to Self-Fitting KeyDevices, of which the following is a specification, taken in connection with the accompanyin'g drawing, which forms part of'the same.

Some of the broad subject matter has been transferred from this case to a'pplicants copending case Serial No. 573,195, filed July 6,1922. g, 7 f

[This invention relates especially, to selffitting or cutting keys of the usual square or rectangular section and provided'with cutting edges or portions on at least one or more ofthedriving faces of the key, so that it may cut or finish its own'keyway when forcibly inserted or driven into the usualrough'cut keyways in the shaft and other cooperatingwparts. Such keys are 'prefer-. ably formed of hardened and tempered steel which may be advantageously groundtosize after such heat treatment or'otherwise accurately shaped, and on one or more faces of the "key, cuttingedges or ,portions are formed preferably in connection with chip retaining recesses, especially where several cutting edges are formed onthe sarne face edges may be slightly smaller or narrower than the adjacent body of the key, so that the finished cut thus produced is a rather snugor force fit into whichthe key may then be driven to secure still tighter and firmer-engagement between the parts. It is of course of special advantage to have such self-fitting or cutting edges arranged on one or both of the driving faces of the connectingor driving key, so. that an accurate fit is thus automatically secured at these driving faces, the inner and outer faces of the key not being of somuch importance in driving rotating parts from shafts. for example. A, V i

In the accompanying drawing showing in a somewhat diagrammatic way several illustrative embodiments of the invention,

Fig. 1 is a section showingthe use of such a key; and i Fig. 2 is an end View thereof. I F gx3 s an enlarged view partly in sect on showing the key construction in greater detail;'and l v I I g i c F1gs. 4t to 6 show other illustrative forms of keys.

As indicated in Figs. 1 and 2, the or dinary rough slotted or milled keyways 11, 14 maybe formed in any desired way inthe' cooperating parts such as the shaft 12 and the flange and coupling member 15; for example. The self-fitting or cutting key 1 which have one or more cutting edges such as 2, .3 on at least one of the driving faces of the key such as its upper or lower notched edge vasindicated in Fig. 1, becomes active in resisting the torque between these sirable to form such self fitting cutting keys oftoolsteel' or still better of special tough strong steel, which is heat treated to harden and toughen the body of the key and leave the cutting edges in most efi'ective condition' In many cases t is desirable to prelimi narilyor roughly form these cutting edges and then lifter hardening and tempering the key, to grind or otherwise finish or straighten the key body, and in some cases to grindthe cuttingedges in proper rela tion thereto to get best results.

As is indicated in Fi'g. 3' one or moire-cutting edges such as 2, 3 may in many cases be advantageously formed on both ofthe opposing driving faces of thekey, and each of these successively acting cutting edges may be slightly larger, so that eachof them may remove a few thousandths of an'inch from the corresponding face oredge of'the keyway as the. key is driven home. It is sometimes advantageous to-have the final cutting edge such as 3 so formed as, to take only a light out, this material being accommodated in a chip retainer recess such as 6 formed adjacent this cutting edge and extending inward, so as to give ample room to produce the desired cutting angle for this edge. In some cases also one or more outtingedges such as 5 may beformed on one or both of the other faces of the key besides the driving faces thereof, although it is usually better to have at least one of these inner and outerkey faces flat so as to act somewhat more efficiently as a guide and aligningsurface w'lienthe key is inserted; In some cases also the keybody mayhave a wedging action if the final cutting edge is slightly smaller than the adjacent driving face of the key, and as shown on an eXag-. gerated scale in the width of the portions 8 of the key adjacent the cutting edges 8 may be slightly smaller than the corresponding driving faces 9; and the inclined or curi' edportion 7 joining these twofaces may have a few thousandths of an inch or less difference in outward projection at its two ends so as to secure the desired tightness of drive fit depending of course on the size of key employed.

Fig. at shows another illustrative'key 16 which may have the, opposing driving, faces 19 and cutting edges 21 on both sides of the key, which may if desired be slightly narrower than the driving faces, the adjacent portions 18 being not more than several thousandths of an inch smaller than the driving faces and joined therewith by the inclined or wedging surfaces 17, so that after the driving faces of the 'keyway have been cut or finished, the key is tightly wedged, or forced into the same to more securely connect the parts, which is desirable in many cases.

This invention has been described in con nection with a number of illustrative embodiments, forms, shapes, proportions, sizes, materials, and arrangements, to the details of which disclosure the invention is not of course to be limited since what is claimed as new and what is desired to be secured. by Letters Patent is set forth in the appended claims: i

1. In self-fitting driving keys, a rectangular sectioned key of hardened steel having on each of its opposite driving faces a plurality of cutting edges of progressively increasing width, the final cutting edges being of slightly less Width than the distance between the driving faces and being oined therewithby an inclined wedging surface to give a drive fit asvthe key is driven or forced into a rough finished keyWay.

2. In self-fitting driving keys, a rectangm posite driving faces a cutting edge of slightly less distance from the opposing driving face than the Width between the drivingfaces and being oined therewith by a Wedging surface togive a drive fit as the keyis driven into an undersized keywayij 1 d. In self-fitting driving keys, a key havington each of its opposite driving faces a cutting edge'of slightly less distance from the 'opposing driving face than the width between the driving faces to give a drive fit as the key is 'dri'venintc an undersizedkeyway.

5. In self-fitting driving keys, arectangular' sectioned steel key having on one of its opposite key faces a cutting edge at slightly less distance from the opposing key face than the width between the key faces' to give a drive fit as the key is forcedinto a rough finished keyway."

6. In self-fitting driving keys, a rectangular sectioned key having onits opposite drive ing, faces cutting edges of several thousandths of an inch lesswvidth than the driving faces and being joined therewith by an inclined wedging surface to give a drive fit as'the'key is driven or forced into a rough linishedfkeyvvay. I

7 In self-fitting keys, a key having on one of its opposite faces, a cuttingedge at a few thousandths of an inch less distance from the opposing driving face than the distancebetween the rear portions of faces, said cutting edge being joined to the cooperating face by anjinclined surface to give a close fit as the key is driven into an undersized keyway, l

8. In self-fitting keys, :1 key having on one of its opposite faces, a hardened cutting edge at slightly less distance from the opposing driving face than the distancebetween'the rear portions of said faces to give a drive fit as the key is driven into an undersized keyway.

9. In self-fitting keys, a key having on one ofits opposite faces, a cutting edgeat slightly less 1 distance from. the opposing driving face than the distance between rear portions of said faces.

ROBERT A. SMITH. 

